Down syndrome FAQ

What is Down syndrome?Down syndrome is a genetic condition where all, or most, of the cells contain an extra copy of Chromosome 21. The most important thing to know about people with Down syndrome is that they are more like other people than they are different.Is there more than one type of Down syndrome?There are three types of Down syndrome. The most common type of Down syndrome, often referred to as Trisomy 21, occurs in approximately 95% of the cases of Down syndrome. In this, all the cells of the body have a third copy of Chromosome 21, giving the person 47 chromosomes instead of 46.Translocation Down syndrome occurs in 3-4% of the cases of Down syndrome. In Translocation Down syndrome a part of the Chromosome 21 breaks off and attaches itself to another chromosome. Often this is Chromosome 14. While the cells will have 46 chromosomes, they will each have an extra piece of Chromosome 21. Mosaic Down syndrome is the rarest form of Down syndrome and occurs in about 1-2% of all people with Down syndrome. In this type of Down syndrome the error in separation of the 21st chromosome occurs in one of the first few cell divisions after fertilization. This results in some cells with 46 chromosomes and some with 47. Because of the fact that not all cells contain the extra Chromosome 21, the range of Down syndrome characteristics varies.Regardless of the type of Down syndrome a person may have, all people with Down syndrome have an extra, critical portion of Chromosome 21 present in all or some of their cells. This additional genetic material impacts development and causes the characteristics associated with Down syndrome. How common is Down syndrome?Down syndrome is the most commonly occurring, and best know, chromosomal condition. Approximately one in every 700 live births in the United States is to a baby with Down syndrome. There are over 400,000 people living in the United States with Down syndrome.Down syndrome occurs in all ethnic, racial, and religious groups, in both genders, and across all socioeconomic levels.When a woman has a child with Down syndrome, her chances of having another child with Down syndrome increases to 1%.Are more children with Down syndrome born to older women?The chances of having a child with Down syndrome increase with maternal age. However, due to higher fertility rates in younger women, approximately 80% of children with Down syndrome are born to women under the age of 35.Did one of the parents do something wrong to have a child with Down syndrome?No, Down syndrome is a chromosomal condition. There is absolutely nothing either parent did, or did not do, either before conception, or during pregnancy, to cause their child to have Down syndrome. What causes Down syndrome?The human body is made of cells and every cell contains all of the genetic information (DNA) for the body. The DNA makes up our chromosomes and contains the code for every gene that is passed from parents to children. Our cells read the DNA and make proteins from the codes and these proteins are responsible for everything from growth to repair, from digestion to the immune system.There are 23 pairs of chromosomes for a total of 46 in every cell. In every person, half of the chromosomes came from their father and half from their mother. When sperm and egg cells are produced, the chromosomes in the cells separate so that there is one complete set of 23, but they are completely mixed in terms of the father’s and the mother’s chromosomes. That is, every egg and sperm that you or I produce has a random assortment of our father’s and mother’s chromosomes.Occasionally, when chromosomes are separating during cell division, an additional chromosome or part of a chromosome may end up in a sperm or egg cell. Down syndrome occurs when Chromosome 21 does not separate evenly during cell division and a child has all or part of three 21st chromosomes. There are three forms of Down syndrome. The most common is Trisomy 21 which means a person has three full copies of Chromosome 21 for a total of 47 chromosomes in every cell. In Translocation Down Syndrome, a portion of Chromosome 21 breaks off during cell division and attaches to another chromosome, usually Chromosome 14. The total number of chromosomes is still 46, but the additional portion of Chromosome 21 results in the characteristics associated with Down syndrome.Mosaic Down Syndrome occurs when typical egg and sperm are produced, but incomplete separation of Chromosome 21 occurs in a later cell division after the egg has been fertilized. When this happens, a portion of the cells of the body will have 46 while others have 47. A person with this form of Down syndrome may exhibit only a few of the characteristics seen in the other forms.What is nondisjunction?Nondisjunction is scientific term for chromosomes not separating properly during cell division. If you want a slightly more scientific explanation of nondisjunction and Down syndrome, please continue reading this answer.The human body is made of cells. All cells contain a center, called a nucleus, in which genes are stored. Genes, which carry the codes responsible for all our inherited characteristics, are grouped along rod-like structures called chromosomes. Normally, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. During cell division (mitosis and meiosis) chromosomes separate and move toward opposite poles. This is referred to as disjunction and results in sister cells each containing 23 pairs of chromosomes. Occasionally, nondisjunction occurs, where the chromosomes do not completely separate, leaving sister cells with one extra and one fewer chromosomes. Down syndrome occurs when the nondisjunction occurs with Chromosome 21.Meiosis is a special type of cell division used to produce our sperm and egg cells. Meiosis produces genetically unique haploid cells, which contain one copy of each of the 23 chromosomes containing a unique mixture of maternal and paternal DNA. When nondisjunction occurs in meiosis you have a cell with 24 chromosomes and one with 22. The most common form of Down syndrome (Trisomy 21) occurs when a sperm or egg with an extra Chromosome 21 joins together with a sperm or egg with 23 chromosomes. This results in a fertilized egg with 47 (instead of 46) chromosomes. With each cell division the extra Chromosome 21 is replicated in every cell of the body.Robertsonian translocation occurs when the long arm of Chromosome 21 is attached to another chromosome, often Chromosome 14. Translocation Down syndrome can occur at the time of an individual's conception, or may be inherited from a parent with a balanced translocation. In balanced translocation an individual has two copies of everything on Chromosome 14, and two copies of all of the material on the long arm of Chromosome 21, but only one copy of the material on the short arm of Chromosome 21 )but this appears to have no discernible effect.) Individuals with this chromosomal arrangement are phenotypically normal. During meiosis the chromosomal arrangement of balanced translocation interferes with the normal disjunction of chromosomes. When a sperm or egg with a translocated Chromosome 21 is combined with a sperm or egg containing 23 chromosomes, it results in a child with translocation Down syndrome.Mosaic Down syndrome occurs when the nondisjunction of Chromosome 21 occurs after fertilization. During the development of the fetus, and through our lives, cell division occurs in process call mitosis. During one of these cell divisions shortly after fertilization, nondisjunction of Chromosome 21 occurs, resulting in a cell with 47 chromosomes. Both the cells with 46 and 47 chromosomes will continue to divide; resulting in portion of the cells of the body will have 46 chromosomes while the remainder will have 47. Is Down syndrome contagious?No, Down syndrome is not a disease, it is a chromosomal condition. People are born with Down syndrome, no one can “catch it” later in life.Is there a vaccine you can take to cure or prevent Down syndrome?No, there is not a vaccine to prevent or cure Down syndrome. However, medical advances have lessened the impact of medical conditions, while early intervention, therapy, education, and support from family and friends, assist the person in leading a productive life. Is Down syndrome inherited?Most of the time, Down syndrome isn't inherited. It's caused when Chromosome 21 does not separate normally in cell division during the development of the egg, sperm or embryo. Translocation Down syndrome is the only form of the disorder that can be passed from parent to child. However, only about 4 percent of children with Down syndrome have translocation. And only about half of these children inherited it from one of their parents. When translocations are inherited, the mother or father is a balanced carrier of the translocation, which means he or she has some rearranged genetic material, but no extra genetic material. A balanced carrier has no signs or symptoms of Down syndrome, but he or she can pass the translocation on to children. What is the life expectancy for someone with Down syndrome?Once the life expectancy of a person with Down syndrome was under 25. Due to an increased understanding of Down syndrome and advances in medical care the current life expectancy for a child born with Down syndrome is 60.How is Down syndrome diagnosed?The diagnosis of Down syndrome is based on the presence of an extra 21st chromosome on a karyotype.What tests are performed to check for Down syndrome?During pregnancy there are two types that can be performed, screening tests, and diagnostic tests. Screening test cannot provide a diagnosis of Down syndrome, but indicate the risk of having a child with Down syndrome compared to other women the same age. There are two types of screening tests used to predict the risk of having a child with Down syndrome, ultrasound (sonogram) tests and blood (serum screening) tests.Some markers (characteristics that some researchers feel may have a significant association with Down syndrome) shown on ultrasound that may indicate an increased risk of a baby having Down syndrome are a decrease in femur length (a bone in the leg), an increase in the skin behind the neck (called nuchal translucency), choroid plexus cysts (cysts in a section of the brain that produces spinal fluid, heart defects, and gastrointestinal defects.Because a mother and her fetus share a circulation system, it is possible to look for certain substances made by the fetus in the mom’s bloodstream. By measuring the amount of these substances at a specific point in pregnancy, it is possible to estimate the risk for the baby to have Down syndrome. There are now numerous different maternal serum screening tests some of which are done in the first trimester and some of which are done in the second trimester. An integrated screening uses a combination of ultrasound findings and blood screening to generate an estimate of the chance for the baby to have Down syndrome. There are three diagnostic tests that can be performed prenatally to conclusively determine if a fetus has Down syndrome. Each of these tests carries a risk of miscarriage. If you are concerned about the possibility of a miscarriage, you should discuss these risks with your OB/GYN or geneticist.Amniocentesis is a test where a sample of the amniotic fluid surrounding the fetus is withdrawn through a needle inserted into the mother's uterus. This sample is then used perform a karyotype. This test is usually performed after 1 weeks of gestation.Chorionic villus sampling (CVS) is a test where cells taken from the mother's placenta can be used to perform a karyotype. This test is typically performed between the ninth and 14th week of pregnancy.Percutaneous umbilical blood sampling (PUBS) is a test where blood taken from a vein in the umbilical cord is used to perform a karyotype. Doctors generally perform this test after 18 weeks of gestation. This test carries a greater risk of miscarriage than does amniocentesis or chorionic villus sampling. Generally, this test is only done when results of other tests are unclear.After a child is born, if there are physical characteristics that indicate a baby may have Down syndrome, a sample of the baby’s blood is drawn and used to perform a karyotype.What is a karyotype?A karyotype is simply a picture of a person's chromosomes. In order to get this picture of the chromosomes, a sample is taken, the chromosome are isolated, stained, and photographed, typically during cell division when the chromosomes are highly visible. A geneticist cut up and arranges the chromosomes from the picture, matching up the pairs and organizing them in rows so that they can be clearly visualized. Depending on the type of staining and imaging used, varying levels of detail are visible. A karyotype can be made from the cell of an adult, a child, or from cells taken from a fetus for the purpose of diagnostic testing.Below is a picture of a karyotype of a male with Down syndrome. You can note the presence of an extra chromosome 21.What are some common physical features of people with Down syndrome?A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, smaller and lower set ears, a smaller nose and mouth, a slightly protruding tongue, increased flexibility, a slightly larger gap between the big and second toes, and a single deep crease across the center of the palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all.What are some common medical problems for people with Down syndrome?People with Down syndrome have an increased risk for certain medical conditions such as congenital heart defects, respiratory issues, hearing problems, vision problems, gastrointestinal and digestive problems, sleep apnea, Alzheimer's disease, childhood leukemia, and thyroid conditions. Many of these conditions are now treatable, so most people with Down syndrome lead healthy lives.Every person with Down syndrome is a unique individual and may possess these conditions to different degrees or not at allWhat are developmental delays?Each person is unique and develops at their own pace. As children develop (as opposed to physical growth) they will be able to perform more complex tasks. Areas of development are Gross motor: using large groups of muscles to sit, stand, walk, run, etc., keeping balance, and changing positions. Fine motor: using hands to be able to eat, draw, dress, play, write, and do many other things. Language: speaking, using body language and gestures, communicating, and understanding what others say. Cognitive: Thinking skills: including learning, understanding, problem-solving, reasoning, and remembering. Social: Interacting with others, having relationships with family, friends, and teachers, cooperating, and responding to the feelings of others.Developmental milestones are a set of skills or tasks that are usually able to be performed at a certain age. Your pediatrician may use milestones to determine how your child is developing. Children with Down syndrome will typically have a developmental delay, meaning they will not reach developmental milestones as quickly as their “typically developing” pears. However, every child is unique and develops at their own pace. Development may be enhanced by early intervention, therapy, and most importantly by supportive family and friends.What is an intellectual disability?Like all people, people with Down syndrome learn at their own rate and in their own way. The impact of having an intellectual disability varies considerably, just as the range of abilities varies considerably among all people. Most people with Down syndrome with have an intellectual disability in the mild to moderate range.Can people with Down syndrome form close personal relationships?Like all people, people with Down syndrome can socialize, have close meaningful friendships, date, and marry.Can people with Down syndrome have children?Infertility and miscarriage is greatly increased in women with Down syndrome, but it is still possible for them to have children. The likely hood of them having a child with Down syndrome is approximately 50%.There are only a handful of documented cases of a male with Down syndrome fathering a child. Can people with Down syndrome be a productive member of society?People with Down syndrome attend schools, live independently, make decisions that affect them, work, volunteer and contribute to society in many ways.Are people with Down syndrome always happy?No. People with Down syndrome have the same range of feelings, emotions, and moods as everyone else.What is the history of Down syndrome?The Jaguar Children (Were-Jaguar), depicted in the carving and art work of the Olmec civilization (1500 BCE – 400 BCE), have many physical characteristics associated with Down syndrome. The Jaguar Children were said to be the result of the birth of a child with an Olmec mother and a jaguar (regarded as a deity) father. These near deity Jaguar Children held a special place in the Olmec culture.Also, the painting The Adoration of the Christ Child, circa 1515, by an unknown Flemish artist, shows one of the angelic figures next to Mary, and a shepherd standing one row back, having many of the physical characteristics associated with Down syndrome.The first clinical descriptions of the condition appear in the 1830s by Jean Etienne Dominique Esquirol (France) and Edouard Seguin (France).Dr. John Langdon Down (United Kingdom), for whom Down syndrome is named, published a report in 1866 in that linked a set of physical characteristics to decreased intellectual ability and lumped it together as a syndrome.The 1930s saw a Dutch ophthalmologist named Dr. Waardenburg promote the idea that genetics might contribute to Down syndrome, and Adrian Bleyer (United States), suggested the possibility that Down syndrome was due to the triplication, called a trisomy, of a chromosome.Working independently Patricia Jacobs (United Kingdom) and Jerome Lejeune (France) reported an extra 21st chromosome in the DNA of people with Down syndrome almost simultaneously in 1959.In 1960 Dr. Paul Polani discovered some instances of Down syndrome were associated with the translocation of the 21st chromosome. In 1961 Dr. Clarke reported the first case of Mosaic Down syndrome.Is it Down syndrome or Down’s Syndrome?Many medical conditions and diseases have been named after a person; this type of name is called an eponym. There has been a long-standing debate in the scientific community over whether or not to add the possessive form to the names of eponyms.You may see both the spelling of Down syndrome or Down’s syndrome. In the United States the spelling Down syndrome is preferred since Dr. Down neither had nor owned the syndrome. The “s” in syndrome is not capitalized.What is some language to use and avoid when speaking about Down syndrome?It is preferred to use people first language. For example, you should not use “a Down syndrome child” or a “Down’s child”, instead use “A child with Down syndrome."A person does not suffer from, nor are they afflicted with, a victim of, nor diseased with, Down syndrome. They simply have Down syndrome.While “mental retardation” may be clinically accepted, it is not socially acceptable to use the word “retarded” in any context that may be derogatory. It is preferred to use the term “intellectual disability”. “You are a retard,” or “That’s retarded,” is insensitive and suggests that a person with an intellectual disability is not capeable.